The present invention relates to a means for transferring an image from a belt to an intermediate support means. In particular, to a transfer means for use in electrophotographic devices such as photocopy machines. In general, transfer devices to which the invention relates are well known in the art, for example, U.S. Pat. Nos. 3,630,615 and 4,371,251. However, unlike the present invention, the devices disclosed in the prior inventions do not have belt storage devices. GB Patent Specification No. 20 17 584 A discloses the use of a belt storage device, but does not have a belt guide roller.
The present invention, on the other hand, is provided with a first drive means which moves the belt at a first speed, a second drive means which moves the intermediate support at a second speed, and a pressure means for bringing the belt into intimate contact with the intermediate support. In response to said contact, the belt assumes the same speed as the intermediate support by virtue of the frictional forces, and the image is thereby transferred from the belt to the intermediate support. A storage device is disposed between the drive means and the pressure means which stores the length difference arising from the difference in the belt speed at the first drive means and at the pressure means.
A device having a belt storage device provided with a guide roller freely movable in one direction is shown in U.S. Pat. No. 4,183,658. However, the disadvantage of the device described therein is that only images of restricted length can be transferred with it, because of the finite storage capacity of the belt storage device. This is particularly disadvantageous in an image-forming device in which long images have to be transferred, e.g., an image-forming device for copying working drawings, in which the length of the images to be transferred may be as much as one meter or more.
Accordingly, it is an object of the invention to provide a measuring means which delivers a measurement signal which is a measurement of the belt length present in the storage device, and an adjusting means to adjust the second speed dependent upon the length represented by the measurement signal.
Generally, the present invention provides a device for transferring image information present on a belt to an intermediate support, comprising a first drive means which propels the belt at a first speed, a second drive means which propels the intermediate support at a second speed; a pressing element for placing said belt in pressure contact with the intermediate support, whereby said belt assumes the speed of said intermediate support and transfers the image information from said belt to the intermediate support; a belt storage device disposed between the drive means and the pressing element for storing the length difference arising from the difference in the belt speed at the first drive means and at the pressing element, a measuring device to provide a measurement signal which is a measurement of the belt length present in the storage device and an adjusting means which adjusts the second speed in dependence on the length represented by the measurement signal.